1. Field of the Invention
The present invention relates to an evaporated fuel treatment device for internal combustion engine, and more particularly to an evaporated fuel treatment device for preventing evaporated fuel generated in a fuel tank from being released into the atmosphere.
2. Background Art
Japanese Patent Laid-Open No. 2001-165003,for example, discloses an evaporated fuel treatment device that includes a canister communicating with a fuel tank. This device has a sealing valve for tightly sealing the fuel tank in a path that makes communication between the fuel tank and the canister. The sealing valve is controlled in a closed state except during refueling. When a refueling operation is detected, the sealing valve is kept in an opened state during a time period between the detection and completion of the refueling.
Given that the sealing valve opens at the time when the refueling operation is detected, a gas in the tank containing evaporated fuel can be emitted toward the canister before a refueling port opens. If the sealing valve is kept opened during the refueling, the gas in the tank can be emitted toward the canister during the time, thus achieving good refueling properties. In such a situation, the canister adsorbs the evaporated fuel contained in the gas in the tank. This prevents the evaporated fuel from being released into the atmosphere as the gas in the tank is emitted.
Provided that the sealing valve is closed in situations other than the refueling, the evaporated fuel is prevented from flowing into the canister in such situations, thus allowing sufficient fuel adsorption space to be always left in the canister to provide for refueling. Therefore, the conventional device can minimize the capacity of the canister required for preventing the evaporated fuel from being released into the atmosphere during refueling, and avoid an increase in size of the canister.
However, in the conventional device, tank internal pressure may become excessively high while the sealing valve is closed. In a state where such high tank internal pressure is generated, it is necessary to open the sealing valve simultaneously with the detection of the refueling operation, and then prohibit opening of the refueling port for a long time until the tank internal pressure is sufficiently reduced, in order to prevent the evaporated fuel from being released into the atmosphere associated with the refueling. Thus, the conventional device effectively prevents the evaporated fuel from being released into the atmosphere, but requires a long waiting time before the refueling in order to make full use of its function.
Such a waiting time can be reduced by, for example, opening the sealing valve at a time when the tank internal pressure increases to a certain extent, and appropriately releasing the tank internal pressure toward the canister. If such a method is used, however, the canister adsorbs the evaporated fuel emitted from the fuel tank when the tank internal pressure is released, and insufficient adsorption space may be left in the canister when the refueling is performed. Thus, a combination of the conventional device and the above described method cannot allow reduction in the waiting time during the refueling while keeping good emission properties.
The present invention is achieved to solve the above described problem, and has an object to provide an evaporated fuel treatment device of an internal combustion engine that achieves good emission properties, and avoids a long waiting time before refueling, using a canister with a minimum capacity.
The above object of the present invention is achieved by an evaporated fuel treatment device of an internal combustion engine. The device includes a vapor passage that makes communication between a fuel tank and a canister. The device also includes a purge passage that makes communication between the canister and an intake passage of the internal combustion engine. A sealing valve is provided to the vapor passage for controlling a communication state thereof. A purge control valve is provided to the purge passage for controlling a communication state thereof. The device includes a tank internal pressure detection unit that detects tank internal pressure. The device also includes a purge control unit that controls the purge control valve to flow evaporated fuel into the intake passage during operation of the internal combustion engine. The device further includes a sealing valve synchronization control unit that opens or closes the sealing valve depending on whether a predefined purge is performed in an area where the tank internal pressure is positive.
Other objects and further features of the present invention will be apparent from the following detailed description when read in conjunction with the accompanying drawings.